Cheers Pitlamp..I was gonna make a reference to Simpson's pot or that I'd see you up at Gaping Ghyll but I fear you might chuck me down the hole.
Anyway, this is not quite as obscure as the last..hopefully clues may not be needed.
Lower Sunset / the other entrance, not sure if they’re the same thing(?). The one just to the right of the path at a bend before the gate with the sheepfolds.
OK, more clues - further to the original post saying "many of you will have been past it, or at least within 10 m" you probably weren't in caving gear at the time.
Oh - and it's a sink rather than a rising. Part of the Ribble catchment.
The exit from Borrins Moor then you can follow the stream and pop back underground by going down the spout into Doctor Bannister's Handbasin and on into Long Churn? (not sure of the name)